Secure systems, including encryption systems, are vulnerable to cryptographic attacks. Secret, cryptographic “keys” used to communicate information between intra-system components (and even extra-system components) and various other circuit operations can be determined by monitoring the power supply currents of the system as well as by way of complex mathematic means to deduce the secure information attributes. To prevent secure information from leaking to the integrated circuit power supply, it is necessary to isolate the secure logic in a way that prevents or greatly attenuates measurable indications of the energy required to operate the secure network.
The energy required to operate the secure network is typically in the form of current impulses that charge or discharge node capacitance present at a logic gate output. Logic gates simply determine whether a node is pulled high (to the positive supply rail) or low (to the negative supply rail) dependent on the inputs to the logic gate. If a node is pulled high, then an impulse current from the positive supply is provided to charge the capacitance at that node to a high value. If a node is pulled low, then the charge present on the capacitor is discharged to the negative supply and is visible as a current impulse. These current impulses may be used by attackers to deduce secure information.